The Arvoredo archipelago (27°17' S; 48°28' W) is formed by three islands (Arvoredo, Galés and Deserta) and a rocky outcrop (São Pedro), which are part of the no-take area named Arvoredo Marine Biological Reserve (AMBR). This Marine Protected Area (MPA) was designated in 1990 and is the unique of its category in the south-southeast coast of Brazil, legally protecting remnants of the Atlantic Rainforest and a rich marine biodiversity. The reserve has 17,000 hectares (42,000 acres), and is located in the central coast of the state of Santa Catarina, 11 kilometres (6.8 mi) north of Santa Catarina Island and 7 kilometres (4.3 mi) off the continent. The archipelago lies over the continental platform and is characterized by the presence of Precambrian crystalline rock shorelines. The depth throughout the archipelago varies from 5 to 25 metres (16 to 82 ft), rarely deeper than 30 metres (98 ft).

Arvoredo is the largest island 318.6 hectares (787 acres), with highly accident relief and steep coastlines providing sites sheltered from the dominant northern quadrant winds and from the strong southern winds. Along its southern rocky-shore SCUBA diving is permitted, as the shoreline in this area lies outside of the reserve limits.

Galés Island 39.7 hectares (98 acres), the closest to the continent, has the same rocky formation as Arvoredo island, with few scarps and two small islets divided by a 27 metres (89 ft) deep channel from the main island.

Deserta Island 13.2 hectares (33 acres) has a well scarped shoreline which is influenced by strong waves due to its southwest-northeast orientation; its relief is elevated in the northern area, with a strong decline southwards.

A few outcrops can be found in the region, such as Pedra Noceti, Parcel do Boi and Parcel da Deserta. The rocky habitat is characterized by many cavities formed by large boulders and medium-small sized pebbles covered with macroalgae.